Myrtle rust

Myrtle rust is a serious fungal disease that affects plants in the myrtle family. Plants in this family include the iconic pōhutukawa, mānuka and rātā as well as some common garden plants such as ramarama and lilly pilly.

UPDATE – 1 May 2018

New approach being taken to manage myrtle rust

If you think you've seen myrtle rust, don't touch it, take a photo, and call 0800 80 99 66.

Where it has been found

Myrtle rust on ramarama(Lophomyrtus bullata)

Myrtle rust (Austropuccinia psidii) has been found across most of the North Island and upper areas of the South Island. This is consistent with modelling that identified these areas had conditions that were most suited to the myrtle rust fungus.

Taranaki, Auckland, and Bay of Plenty are the most seriously affected areas. Moderate levels of infection are in Northland, Waikato, Manawatu-Whanganui, and Wellington.

Lower levels of infection have been confirmed in Taupo, Tasman, Nelson-Marlborough, Coromandel Peninsula, and the East Cape.

Plants affected

The fungus attacks plants belonging to the Myrtaceae family, also known as the myrtle family.

Most infections have been found on 2 native myrtle types:

ramarama (Lophomyrtus) – used widely for residential hedging

pōhutukawa and rātā (Metrosideros).

A number of other introduced myrtles have also been affected, including lilly pilly (Syzgium) and bottle brush (Callistemon).

During a year of intensive operational activities, owners of properties where infected plants were found were restricted from moving plants and plant material that were known or likely to have been infected. These restrictions are now being progressively lifted.

Myrtle rust continues to be an unwanted organism throughout New Zealand.

Spores can spread easily

Myrtle rust spores are microscopic and can easily spread across large distances by wind, or via insects, birds, people, or machinery.

Evidence suggests the fungus arrived in New Zealand carried by strong winds from Australia where it is well established all down the eastern coast.

The Ministry for Primary Industries (MPI) and the Department of Conservation (DOC), with the help of local iwi, the nursery industry, and local authorities ran a year-long operation to attempt to contain and control myrtle rust and determine the extent of its spread.

Risk to New Zealand

Myrtle rust could affect iconic New Zealand plants including pōhutukawa, mānuka, rātā, kānuka, swamp maire and ramarama, as well as commercially-grown species such as eucalyptus.

Severe infestations can kill affected plants and have long-term impacts on the regeneration of young plants and seedlings.

Myrtle rust is known to produced the teliospore stage in New Zealand. This spore stage is different from the asexual urediniopsore stage and indicates that the fungus is capable of reproducing sexually. Sexual reproduction introduces genetic variability, increasing the risk to New Zealand, as it allows fungi to adapt to new environments and possibly affect new hosts.

It is not yet known how this disease will affect New Zealand species, but myrtle rust will likely continue to affect a wide range of susceptible myrtle plants under New Zealand conditions. Overseas its impacts have varied widely from country to country and plant species to species.

if you have a camera or phone camera, take clear photos, including the whole plant, the whole affected leaf, and a close-up of the spores or affected area of the plant.

Remember, don't touch it or try to collect samples as this may increase the spread of the disease.

Do not attempt to self-treat trees and plants with a fungicide, either for a cure or to try to prevent myrtle rust infection. We are still building a picture of whereabouts the disease is present nationally, and if people use preventative sprays, it could suppress symptoms, and prevent us from making the best management decisions for the country.

Arrive clean, leave clean

The forest you visit could be infected with myrtle rust without you knowing it. Before entering such areas for work or recreation, you should minimise the risk of spreading the rust by ensuring your equipment, clothing, and tools arrive clean and leave the area clean.

Buy healthy plants and prune in cool weather

Make sure myrtle plants bought for your garden are free from the symptoms of myrtle rust. Inspect the leaves and stems of plants before you buy them, and avoid buying plants that have signs of disease. Keeping your plants in the best condition and health possible is likely to improve their resilience and ability to cope with pests and diseases including myrtle rust.

We recommend avoiding heavy pruning during warm weather as this will encourage susceptible new growth. Instead, prune myrtles only in late autumn and early winter to avoid encouraging new growth during warm weather when myrtle rust spores are more likely to form. When pruning, use good hygiene practice, sterilise, and disinfect tools and equipment with pure alcohol or methylated spirits.

Monitor your plants

We recommend regular monitoring of myrtle plants for any sign of myrtle rust, particularly new, young growth, shoots, and seedlings. Early detection in your garden will give you time to consider options for myrtle rust control on your property. If myrtle rust does establish on your property, note which plants become the most severely affected.

Symptoms to look out for

It generally attacks soft, new growth, including:

leaf surfaces

shoots and buds

flowers, and fruit.

Symptoms to look out for on myrtle plants are:

bright yellow powdery eruptions appearing on the underside of the leaf (young infection)

bright yellow powdery eruptions on both sides of the leaf (mature infection)

MPI will continue to help collect, analyse, and report myrtle rust data. The data will allow us to build up the picture of the spread and distribution of infection.

But MPI will no longer be doing field work to manage the disease. Activities like surveillance, and spraying or removing infected trees has stopped.

Landowners with myrtle rust infection on their property can decide how to manage their plants themselves. MPI will continue to provide advice and guidance on what people can do to manage myrtle rust on their own properties.

What you can do

You're still encouraged to continue to report any possible cases of myrtle rust. Phone our biosecurity hotline on 0800 80 99 66. Your calls will help us to:

track the spread and monitor the impacts of the disease

understand any resistance in native species.

Your help is vital to our long-term myrtle rust management and research programmes.

Other long-term planning activities

We are:

engaging with iwi, communities and councils across New Zealand

looking at ways that MPI can support those who wish to do their own biosecurity activities

developing a programme to provide training to support community-based monitoring for interested groups.

We've also established a cross-sector working group. It will provide input and recommendations on agreed goals that will underpin a collaborative long-term management plan across the country.

This group includes members from MPI, Department of Conservation, Ministry for Culture and Heritage, regional councils, Project Crimson, and Māori organisations with an interest in biosecurity.

We'll circulate a draft long-term management strategy and action plan for public comment, before it's finalised in late December 2018.

Research programme

Research is vital to help us understand myrtle rust and limit its impact on our myrtle plants. MPI has commissioned a comprehensive research programme made up of more than 20 projects and valued at over $3.7 million.